Conventional TIG or MIG welding techniques have long been used for welding large masses of metal. These techniques have inherent limitations. Specifically, such techniques require the use of large amounts of heat and frequently result in significant power waste. Further, such techniques frequently result in weak weld because of metal crystalization. These techniques are also highly labor inefficient.
More recently electron-beam welding has been used in place of such earlier technology. In electron-beam welding a collated stream of electrons is directed to the butting portions of the metal masses to be welded. This technique is highly satisfactory in welding comparatively thin pieces of metal together or in welding thicker and heavy masses of metal that have no inherent magnetic field. However, electron-beam welding has inherent limitations in welding heavy pieces of metal that have magnetic fields. In such heavy metal pieces there is a tendency of the electron-beam to skew from the intended path after the beam has passed partially through the metal. This skewing results from the influence of the magnetic field and in turn causes poor and defective welds. This difficulty is particularly acute in welding plates, tubes or other heavy metal pieces in a wide range of industrial uses including, for example, in coal liquification equipment and the like.